ARTIFICIAL PEODUCTIOy OF TUBERCLE. 2'7 



i must confess that the theory advanced by some recent pathologists, 

 since Dr. Cohnheim's researches on the exit of the white corpuscles from 

 the blood-vessels, that the growth of tubercle is a result of this process — 

 a theory, be it remembered, originally to some extent advanced by Dr. 

 Addison of Brighton — does not appear to me to be supported by observa- 

 tions on these growths. The complete obstruction of the vessels in their 

 neighbourhood would militate against this view of their origin ; and a con- 

 siderable amount of evidence may be found in some parts of the growth, 

 that their increase is due to the enlargement and subdivision of pre- 

 existing cell-forms. 



To sum up the conclusions which the facts appear to warrant regarding 

 the origin of this process, I would say that the growths produced appear to 

 originate from an abnormal nutritive activity of tissues either demonstrably 

 lymphatic in their nature, or of those whose lymphatic character is a matter 

 of probable inference ; that this increased growth is caused by septic matter 

 introduced into the system, and especially affecting these tissues by an irritative 

 action ; that the new growths thus produced conform in many particulars to 

 the lymphatic type, but, growing under abnormal conditions, or with perverted 

 activity, they speedily pass into degenerative decay. This action, however, 

 once excited, tends to repeat itself in the economy, either by virtue of the 

 results of such degeneration possessing properties similar to that of the 

 material whose morbid influence first excited the diseased process, or through 

 direct infecting properties of the new growth transmitted either by the blood 

 to distant organs, or, as in the case of the lymphatic glands, by means of 

 infection through the lymphatic vessels. 



This theory of the effects of septic matter is not altogether new. It was 

 originally propounded by Dittrich ' as an explanation of the cause of tuber- 

 culisation, and again by Buhl ; ^ the former of whom believed that the septic 

 infection producing tuberculisation was due to the retrograde metamorphosis 

 of any morbid pathological products ; the latter attributing it only to retro- 

 grade changes in tubercle once produced. It finds, however, for the first time, 

 its direct proof in these experiments. They also illustrate what clinical expe- 

 rience has recently led Professor Niemeyer to assert, that tubercle of the lung 

 may be a secondary consequence of unabsorbed pneumonias.' They illustrate, 

 also, what has been the result of frequent surgical experience, but was first, 

 as far as I am aware, distinctly stated by Mr. Holmes, at the Children's 



1 Virchow, Krank. Gesch., i. 113. ' Klinische vortrage liber die Lungen-Schwind- 



2 Zeitsch. Eat. Med., 1857. sucht. 



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